If method `set_netns` fails, restore previous device namespace

If the ``IpLinkCommand.set_netns`` fails, the method restores the
previous device namespace before raising the exception.

Closes-Bug: #2049590
Change-Id: I73b36ef161441b52922d888c11a144eafe8a7ed0

neutron/agent/linux/interface.py

@@ -374,11 +374,6 @@ class OVSInterfaceDriver(LinuxInterfaceDriver):
                 LOG.warning("Failed to set interface %s into namespace %s. "
                             "Interface not found, attempt: %s, retrying.",
                             device, namespace, i + 1)
-                # NOTE(slaweq) In such case it's required to reset device's
-                # namespace as it was already set to the "namespace"
-                # and after retry neutron will look for it in that namespace
-                # which is wrong
-                device.namespace = None
                 time.sleep(1)
             except utils.WaitTimeout:
                 # NOTE(slaweq): if the exception was WaitTimeout then it means

neutron/agent/linux/ip_lib.py

@@ -25,6 +25,7 @@ from neutron_lib import constants
 from neutron_lib import exceptions
 from oslo_config import cfg
 from oslo_log import log as logging
+from oslo_utils import excutils
 from oslo_utils import netutils
 from pyroute2.netlink import exceptions as netlink_exceptions
 from pyroute2.netlink import rtnl
@@ -477,16 +478,16 @@ class IpLinkCommand(IpDeviceCommandBase):
             self.name, self._parent.namespace, state='down')
 
     def set_netns(self, namespace, is_ovs_port=False):
-        privileged.set_link_attribute(
-            self.name, self._parent.namespace, net_ns_fd=namespace)
-        self._parent.namespace = namespace
-        if is_ovs_port:
-            # NOTE(slaweq): because of the "shy port" which may dissapear for
-            # short time after it's moved to the namespace we need to wait
-            # a bit before checking if port really exists in the namespace
-            time.sleep(1)
-        common_utils.wait_until_true(lambda: self.exists, timeout=5,
-                                     sleep=0.5)
+        old_namespace = self._parent.namespace
+        try:
+            privileged.set_link_attribute(
+                self.name, self._parent.namespace, net_ns_fd=namespace)
+            self._parent.namespace = namespace
+            common_utils.wait_until_true(lambda: self.exists, timeout=3,
+                                         sleep=0.5)
+        except common_utils.WaitTimeout:
+            with excutils.save_and_reraise_exception():
+                self._parent.namespace = old_namespace
 
     def set_name(self, name):
         privileged.set_link_attribute(

neutron/tests/unit/agent/linux/test_interface.py

@@ -13,11 +13,13 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import time
 from unittest import mock
 
 from neutron_lib import constants
 from neutron_lib.plugins.ml2 import ovs_constants as ovs_const
 from oslo_utils import excutils
+from oslo_utils import uuidutils
 from pyroute2.netlink import exceptions as pyroute2_exc
 
 from neutron.agent.common import ovs_lib
@@ -387,6 +389,10 @@ class TestABCDriver(TestBase):
 
 class TestOVSInterfaceDriver(TestBase):
 
+    def setUp(self):
+        super().setUp()
+        self.mock_sleep = mock.patch.object(time, 'sleep').start()
+
     def test_get_device_name(self):
         br = interface.OVSInterfaceDriver(self.conf)
         device_name = br.get_device_name(FakePort())
@@ -525,13 +531,14 @@ class TestOVSInterfaceDriver(TestBase):
         self.ip.ensure_namespace.return_value = namespace_obj
         namespace_obj.add_device_to_namespace.side_effect = (
             ip_lib.NetworkInterfaceNotFound)
-        device = mock.MagicMock()
+        namespace_name = uuidutils.generate_uuid()
+        device = mock.MagicMock(namespace=namespace_name)
         self.assertRaises(
             ip_lib.NetworkInterfaceNotFound,
             ovs._add_device_to_namespace,
             self.ip, device, "test-ns")
         self.assertEqual(10, namespace_obj.add_device_to_namespace.call_count)
-        self.assertIsNone(device.namespace)
+        self.assertEqual(namespace_name, device.namespace)
 
 
 class TestOVSInterfaceDriverWithVeth(TestOVSInterfaceDriver):